American Osteopathic Association

Advancing the distinctive philosophy and practice of osteopathic medicine

Microwaves and Plastics: How to Safely Re-Heat Your Leftovers

Plastics play a crucial role in our kitchens. From storing to serving, there are numerous ways our food comes in contact with plastic every day. The question is: Are all these interactions safe? 

“When certain types of plastic are heated in the microwave, the substances and chemicals used in the manufacturing of the plastic can leak into your food,” explains Rob Danoff, DO, an osteopathic family physician in Philadelphia. “This plastic residual can raise health concerns when ingested, especially in infants and pregnant women.” 

However, that doesn’t mean it’s unsafe to microwav​e all plastics. It depends on the type of plastic and on the type of food you are heating,” says Dr. Danoff. “Fatty foods, like meats and cheeses, reach very high temperatures and may cause the plastic to warp or melt. This in turn has the potential to cause a chemical to seep out of the plastic and into the food.”

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Is It Microwave-Safe?

It’s important to know what to look for when determining if certain plastics are safe for the microwave. “A good place to start is with the manufacturer's labels on your plastic containers,” says Dr. Danoff. 

Every plastic container intended for use with food has to undergo stringent testing performed by the FDA. If a plastic product is determined safe for microwave use, then you will see either a microwave-safe symbol or written instructions indicating the product is microwave-safe. The numbering system found on plastics pertains to recycling and does not indicate whether or not the plastic is safe for heating. 

However, Dr. Danoff warns that not all microwave-safe products are safe to use in the microwave in the same way. 

What About Plastic Wrap?

Although certain types of plastic wrap are approved by the FDA as microwave-safe by the FDA, they can melt if they come in direct contact with hot food. 

Dr. Danoff recommends leaving at least one inch between plastic wrap and food before heating, or using alternatives like wax paper, parchment paper, or white paper towels.

Microwave Dos and Don'ts

According to Dr. Danoff, certain types of plastic should always be avoided when heating food in a microwave. These include: 

  • Restaurant takeout containers

  • Water bottles

  • Plastic tubs and jars made to hold margarine, cream cheese, yogurt, mayonnaise, mustard, etc.

  • Plastic storage bags or plastic bags from the grocery store  

Dr. Danoff also encourages the following microwaving tips:

  • Never reheat the plastic tray formulated for frozen dinner and lunch entrees. These are intended for one-time use only.     

  • Vent the container when microwaving by leaving the lid ajar or lifting the edge. 

  • Ensure your product states “microwave safe” or contains instructions for use in the microwave.

“The important thing is to always read the labels of your plastic containers carefully before you put them in the microwave,” cautions Dr. Danoff. “If you are unsure, then it's best to heat your food in a microwave-safe container made of a different material, such as glass or ceramic.” ​​​​​​

 

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